1. Technical Field
The present disclosure relates to sensing and reconstructing digital signals of a high-speed circuit for capture and analysis in external test equipment.
2. Background Information
Conventional oscilloscope probes (“scope probes”) are generally difficult to use for sensing electrical characteristics of digital signals of a high-speed circuit, such as a high-speed serial bus connecting a plurality of integrated circuits (ICs) on a printed circuit board. Although they may be available in a variety of different impedances, these scope probes generally load the high-speed circuit to which they interface in different ways and to differing amounts. That is, even probes that delicately disturb a signal may distort the waveform. Because of such disruptive loading, it is thus generally difficult to sense and analyze the high-speed digital signals using the conventional scope probes.
In addition certain factors, such as length of a circuit board trace, whether the trace crosses a boundary in a ground plane of the circuit board and/or whether there are other traces near by, can affect the operation of the high-speed circuit to its detriment, resulting in cross talk, impedance changes, and/or reflections. It is therefore desirable to test for such factors using a commercial version of the high-speed circuit so as to enable any needed debugging. This is particularly true for high-speed serial bus circuitry because its signal paths are treated as transmission lines. However, the serial bus circuitry is often a fine pitch implementation between the ICs and, as such, there is very limited distance on the serial bus for an operator, such as an engineer, to work. Accordingly, there is typically no provision within the implementation for sensing the high-speed digital signals for testing and debugging by external test equipment in normal operation.